Fibromyalgia Overview

Fibromyalgia (FM) is a common, chronic, generalized pain syndrome of unknown origin. Although pain and tenderness are its defining features, fatigue, sleep disturbance, non-cardiac chest pain, depression and poor concentration are also common. FM is second only to osteoarthritis in frequency of visits to rheumatology clinics, and about 5% of women and 0.5% of men in the United States will be affected, and the majority will be between 30 to 50 years of ageref 1.

Although diffuse pain and tenderness are its defining characteristics, over 75% also report chronic fatigue, a major contributor to the disability and impairment in FMref 2. FM also associates with a variety of health problems including sleep disturbance, irritable bowel syndrome, and mood disordersref 3. Although it is unclear whether persons with FM are more likely to have a psychiatric disorder than the general population, it is estimated that 20% to 40% of persons with FM experience mood disorders such as depression and anxietyref 4. This is not surprising given the multiple symptoms, normal laboratory tests, feelings of victimization, loss of control, and generally ineffective treatments. Moreover, routine tasks take longer to accomplish, and adaptations must be made to minimize pain and fatigue that negatively affect employment and social activitiesref 5.

Due to the constellation of symptoms associated with FM its impact can be severe. It associates with poorer quality of life than rheumatoid arthritis, type 1 diabetes, and chronic obstructive pulmonary diseaseref 6. Moreover, it often promotes physical inactivity, social withdrawal, and psychological distress. FM also occurs commonly in patients with other rheumatic diseases, especially rheumatoid arthritis and lupusref 3. One patient recently referred to their FM as, “A body toothache that stays with me all the time.”

Pathophysiology

Although the cause or causes of FM remains to be determined, most researchers believe that the widespread pain, the hallmark symptom of FM, is due to abnormalities in central nervous system function. Moreover, it has been hypothesized that aberrations in the stress response (i.e., corticotrophin-releasing hormone and locus ceruleus-norepinephrine/autonomic nervous systems) may play an important role in symptom expression. Finally, given the prevalence of emotional/mood disorders in persons with FM, it is also thought that psycho-behavioral factors may contribute to the pathogenesis and/or individual expression of FMref 3.

With regard to nervous system function, it is thought that persons with FM experience pain amplification due to abnormal sensory processing in the central nervous system. This is supported by studies showing multiple physiological abnormalities in persons with FM, including: increased levels of substance P in the spinal cord, low levels of blood flow to the thalamus region of the brain, low levels of serotonin and tryptophan and abnormalities in cytokine functionref 5.

It has also been suggested that FM may relate to an abnormality in deep sleep. That is, abnormal brain waveforms have been found in deep sleep in many persons with FM. Moreover, tender points can be produced in normal volunteers by depriving them of deep sleep for a few days. By the same token, levels of growth hormone, important in maintaining good muscle and other soft tissue health, and produced almost exclusively during deep sleep, have been found to be low in persons with FMref 3.

Finally, recent studies show that genetic factors may predispose individuals to a genetic susceptibility to FM. For some, the onset of FM is slow; however, in a large percentage of persons the onset is triggered by an illness or injury that causes trauma to the body. These events may elicit an undetected physiological problem already presentref 7.

References

Wolfe, F et al. Prevalence of characteristics of fibromyalgia in the general population. Arthritis and Rheumatism38:19-28, 1995.

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